Where recording equipment and data analysis equipment are mismatched, as with a multi-channel tape recording unit providing data to a single or dual channel input computer an effective means of comparing input signals occurring at the same time on different channels is difficult. To match the equipment by having the same number of input channels on the computer as output channels on the recorder can be expensive.
Further, where the events to be recorded are of a scientific or engineering kind and occur randomly at large intervals of time a sophisticated means of time identification is needed to identify the signals on different channels coming from the same source. For example, in monitoring explosions with multiple channel recording equipment and subsequently analyzing all data on all channels needs an accurate means of locating corresponding signals on each channel.
The invention can be used in numerous environments wherein the time of occurrence of an event may not be known, or wherein it may be too difficult to provide an accurate signal at the beginning of the event. Examples of such situations would include military situations wherein some event is under surveillance but the time at which it will occur is unknown. Another situation is in blasting wherein a remote monitoring station is provided, and it is too difficult or too dangerous to time the operation of the monitoring means into the circuitry of the blasting equipment itself. During the blasting, ground movement can be computed to ascertain possible damage to nearby buildings. Another application of the invention could be in seismic work, where the resultant wave form of the reflected wave caused by the explosion needs to be accurately produced.
Many prior art systems depend upon a timing pulse which occurs at the time of the firing of the explosive. This method is undesirable because it requires wiring into the firing circuit, radio transmission of start signals, cable runs, or the like. All of these problems are eliminated with the invention.